(1) Field of the Invention
This invention relates to negative battery electrodes composed of finely divided active materials. A preferred aspect of this invention relates to negative electrodes for ambient temperature nonaqueous secondary batteries composed singly or in combination of conjugated backbone polymers and alkali metal alloying or alkali metal ion inserting materials.
(2) Prior Art
The use of elastomeric binders for cathodes are known. For example, S. P. S. Yen, et al., "Elastomeric Binders for Electrodes," J. Electrochem. Soc., 130, p. 1107 (1983) describes the use of ethylene propylene diene terpolymer as a binder for cathodes. In particular, cathodes for which elastomers are useful as binders are finely divided alkali metal intercalation compounds. Examples of intercalation compounds are found in European patent No. 0070107 A1; Murphy et al., J. Electrochem. Soc., 126, 349 (1979) and Murphy et al., Mat. Res. Bull., 13, 1395 (1978) which disclose batteries based on lithium intercalation in layered dichalcogenides.
Negative electrodes for non-aqueous batteries composed of alkali metal alloys are known. For example, U.S. Pat. No. 4,002,492 discloses electrochemical cells having an anode consisting essentially of lithium aluminum alloys that contain lithium in amounts between about 63% and 92% and the balance essentially aluminum. Anodes composed of lithium and aluminum are also disclosed in Rao, et al., J. Electrochem. Soc. 124, 1490 (1977), and Besenhard, J. Electroanal. Chem., 94, 77 (1978).
Conjugated backbone polymers, e.g., polyacetylene, polyphenylene, polyacenes, polythiophene, poly(phenylene vinylene), poly(alkoxyphenylene vinylene), poly(furylene vinylene), poly(thienylene vinylene), polyazulene, poly(phenylene sulfide), poly(phenylene oxide), polythianthrene, poly(phenylquinoline), polyaniline, polythiophene, and polypyrrole, have been suggested for use in a variety of applications based upon their characteristic of becoming conductive when oxidized or reduced either chemically or electrochemically. The secondary btttery application described by, e.g., MacDiarmid et al. in U.S. Pat. No. 4,321,114 (1981); J. de Physique, Colloque C3, Vol. 44 (1983), articles beginning on page 579, page 615 and page 537; and K. Kaneto et al., Japanese J. of Applied Physics, Vol. 22, pp. L567-L568 (September 1983) and pp. L412-L414 (July 1983), employs one or more electrodes having conjugated backbone polymers as the electroactive material. Such electrodes can, for example, be reversibly complexed with alkali metal or tetraalkylammonium cations during battery cycling, most commonly with insertion of cations into a polymer anode (the negative battery electrode) occurring during charging. The more such cations are inserted, the more conductive the electrode becomes and the more cathodic the potential of the anode becomes.
Composite structures of a conjugated backbone polymer and a non-electroactive material have been described in U.S. Pat. No. 4,294,304 and in the above J. de Physique issue, articles beginning on page 137 and on page 151. Representative other components that have been blended with polyacetylene or onto which polyacetylene or polypyrrole have been deposited include polyethylene, polystyrene, graphite, carbon black, NESA glass and silicon. In selected instances, such composite structures have been suggested for use in batteries, see Showa Denko K.K., European published patent application 76,119 (1982). U.S. Pat. No. 4,668,596 described anodes for secondary batteries which comprises a mixture of a conjugated backbone polymer and another electroactive material selected from the group consisting of metals which alloy with alkali metals and alkali metal cation inserting materials as for example, transition metal chalcogenides.